When 1 mM serotonin, dopamine, or norepinephrine was incubated with a monoamine oxidase preparation (mitochondrial membranes) in the presence of 4 mM sodium bisulfite, 85-95% of the amines were oxidized to the corresponding aldehydes. In the absence of bisulfite, the recoveries were only approximately 30%, and dark colored products were formed during the incubations. The aldehydes derived from tyramine, octopamine, methoxytyramine, and normetanephrine were also prepared by the use of this method. The bisulfite-aldehyde compounds were stable during storage at -20 degrees C. Bisulfite-free aldehyde solutions were made by diethylether extraction. When the aldehydes derived from dopamine or serotonin were incubated with rat brain homogenates, they were found to disappear in an aldehyde dehydrogenase- and aldehyde reductase-independent manner. The disappearance of the latter aldehyde was more pronounced, and the results indicated that this aldehyde may react with both proteins and phospholipids.
SUMMARYJuvenile rainbow trout were isolated in individual compartments and allowed to acclimate for 1 week, during which they were fed commercial trout pellets. The feed was then replaced by pelleted feed supplemented with L-tryptophan(TRP) at two, four or eight times the concentration in the commercial feed. Fish were fed these supplemented feeds daily to satiety for 1 week, after which half of the fish were stressed, by lowering the water level for 2 h,while the remaining fish were left undisturbed. In undisturbed fish,supplementary dietary TRP resulted in slightly elevated plasma cortisol levels. In response to the stress, fish that had been fed control feed showed elevated plasma cortisol levels, but fish fed the TRP-supplemented feed displayed a significant reduction in this stress-induced elevation of plasma cortisol levels. Plasma and brain TRP levels were elevated in fish fed TRP-supplemented feed. TRP is the precursor of the monoamine neurotransmitter serotonin. Brain serotonergic activity was elevated by stress and also tended to be increased by elevated dietary TRP intake. The central serotonergic system is involved in the control of the hypothalamic—pituitary—interrenal axis, the action of serotonin being to stimulate or inhibit this neuroendocrine axis through different projections.
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